Field of the Invention
The present invention relates to a fuel cell module including a fuel cell stack formed by stacking a plurality of fuel cells for generating electrical energy by electrochemical reactions of a fuel gas and an oxygen-containing gas, and a casing containing the fuel cell stack.
Description of the Related Art
In general, a solid oxide fuel cell (SOFC) employs a solid electrolyte. The solid electrolyte is an oxide ion conductor such as stabilized zirconia. The solid electrolyte is interposed between an anode and a cathode to form an electrolyte electrode assembly (hereinafter also referred to as the MEA). The electrolyte electrode assembly is sandwiched between separators (bipolar plates). In use, generally, predetermined numbers of the electrolyte electrode assemblies and the separators are stacked together to form a fuel cell stack.
In the SOFC, since the operating temperature is relatively high, in the case where a power generation chamber is provided in a casing, the temperature of the upper part of the power generation chamber tends to be low in comparison with the lower part of the power generation chamber. In particular, in the case where a combustion area is provided above the stack which is placed in the power generation chamber of the casing, temperature of the upper part of the power generation chamber is considerably high in comparison with the lower part of the power generation chamber. Consequently, degradation may occur undesirably at welding positions or attachment positions.
In an attempt to improve the durability of the casing and extend the lifetime of the casing, for example, a fuel cell apparatus as disclosed in Japanese Laid-Open Patent Publication No. 2013-131329 is known. This fuel cell apparatus includes a casing having a first U-plate member and a second U-plate member. The first U-plate member is formed by a first upper surface opening section which is opened upwardly, two first side walls which face each other, and a first bottom plate connecting lower portions of the first side walls. The second U-plate member is formed by a second upper surface opening section which is opened upwardly, two second side walls which face each other, and a second bottom plate connecting lower portions of the second side walls.
The casing is formed by stacking the first U-plate member and the second U-plate member such that the first upper surface opening section and the second upper surface opening section are positioned on the upper side, with a space between the first U-plate member and the second U-plate member in the thickness direction. At least a portion of at least one of a cathode gas channel and an exhaust gas channel includes a side space channel formed by the first side wall and the second side wall which face each other, and a bottom space channel formed by the first bottom wall and the second bottom wall which face each other. The bottom space channel is connected to the side space channel.
Specifically, in Japanese Laid-Open Patent Publication No. 2013-131329 mentioned above, the cathode gas channel is formed in the side space channel and the bottom space channel, and an exhaust gas channel is formed along the inner side of the cathode gas channel. According to the disclosure, in the structure, since the cathode gas in the cathode gas channel is heated beforehand by the exhaust gas flowing in the exhaust gas channel, and the cathode gas as the air having a relatively low temperature flows along outer surfaces of the casing, heat radiation is suppressed.